


Caverna

by floatingbuildings



Category: Final Fantasy XV
Genre: Alternate Universe, Anal Fingering, Anal Sex, Car Sex, First Time, Fluff and Smut, M/M, Sex in a Car
Language: English
Status: Completed
Published: 2018-01-08
Updated: 2018-01-08
Packaged: 2019-03-02 10:56:11
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,867
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/13316643
Author URL: https://archiveofourown.org/users/floatingbuildings/pseuds/floatingbuildings
Summary: Niflheimian Prince Prompto AU, wherein Ardyn takes Prompto somewhere nice and Prompto is not as subtle as he thinks. There is car sex (in the Vixen, not the Regalia). And tooth-rotting fluff.For Promdyn Ship Week, Day One: "Prompto, the Lonely Prince of Niflheim AU."





	Caverna

**Author's Note:**

> I honestly don't know why Ardyn had to bring Prompto out on this weird date, but I do know Ardyn's hideous Ford knockoff car is like an aphrodisiac to me, and so to Prompto. Unbeta'd, please let me know if you spot any mistakes. Come yell at me about FFXV on tumblr @ floatingbuildings!

"Humor an old man." 

Prompto rolls his eyes, taking Ardyn's outstretched hand and steadfastly ignoring how just touching the man's skin makes his stomach flutter. "I swear you haven't aged since I was six years old. I'm pretty sure one of the reasons my father keeps you around is to study you."

"You're too kind," Ardyn says dryly, letting Prompto grip his gloved hand for leverage until they are both at the flatter top of the mountain before dropping it. Prompto is only a little disappointed at the loss of contact. Maybe on the ride back to the castle, he can surreptitiously scooch his way across the Vixen's bench seats until they brush against each other, especially during turns. Not that Prompto's thought about it before. Or imagined how it would feel to lay down on the butter-soft leather with Ardyn on top of him, one leg slid in between Prompto's, arms on either side of his shoulders, face close enough to feel his warm breath that smells like the whiskey he drinks sometimes, sort of smoky...

"Your Highness."

"Oh!" Grateful that he can blame the altitude and the trek for the flush of his cheeks, Prompto blinks and notices that Ardyn is already some distance away. "Sorry! It's really pretty up here, that's all. I should have brought my camera." 

"Perhaps next time." Ardyn waves him onward. "We're nearly there."

He wants to ask where, but Ardyn has always been a _show, don't tell_ kind of person, so he follows that familiar grey coat he's followed all of his life, wondering vaguely how Ardyn is keeping warm despite his many layers; they're not as thick as Prompto's own coat and gloves. Maybe if they stay late enough, they can build a fire on the mountain, and the cold Niflheim evening could be a great excuse to huddle close. It's the kind of romantic thought that makes Prompto's insides feel blood-warm, and he's not really focusing on his surroundings, and while Ardyn is quick to scold such daydreaming, he always does it with fondness...

Prompto runs nose-first into the space between Ardyn's shoulders, and it's a little like running into a solid wall. He touches his nose gently as Ardyn turns, one eyebrow arched at him. 

"Sorry," Prompto apologizes again. And really, isn't it a little weird that he apologizes to Ardyn what seems an inordinate amount, but Ardyn has always said to never apologize to anybody else, because he's the prince and princes, especially Niflheimian princes, do not apologize? 

He realizes they are standing at what appears to be the entrance of a cave. 

"Is that a cave?" The question sounds stupid even as it leaves his mouth, but in his defense, who expects to see a cave at the top of an isolated snow-covered mountain? 

"It is indeed." Ardyn has to duck to enter the opening, one hand on his hat to keep it from snagging. Even Prompto has to bend his knees to go through. "Come, it's only a little farther."

Ardyn uses an elemental spell to light the way through the pitch black tunnel. It's not a tight squeeze by any means, but Prompto would hit either side if he stretched his arms out, and the confinement makes him nervous. The light is somewhat blocked by Ardyn's body, and Prompto stays very close. They walk for a few minutes, and while Prompto is glad to be out of the slight sting of the wind, he can feel tension knotting up his muscles at the combination of the darkness and the restrictive space.

He almost runs into Ardyn's back again, but he's saved from the embarrassment this time by Ardyn's suddenly cheerful voice, echoing as though in an empty chamber: "Here we are, Highness! I hope you like it."

Ardyn steps aside, and there _is_ a chamber, and Prompto's breath catches. 

It's _beautiful._ Maybe the most beautiful thing he's ever seen, and he's seen newborn chocobos, feathers fluffed and little beaks _kweh_ ing softly. 

The tunnel has ended in a room about sixty meters across, and everywhere — on all the walls, the ceiling, even spreading out from where they stand — are what look like crystals, radiating different colors. It's like being inside of a holiday tree strung with softly pulsing lights. 

"Wow!" Prompto bounces on the balls of his feet for a second, before darting forward to touch the crystalline outcroppings on the nearest wall. He can feel how sharp they are even though this thick gloves, but they're smooth in some places too, multicolored and fading into deeper rainbow hues where they meet the dark rock. "What are they? What makes them glow like that? How did you find this place?"

His excited questions echo and so does Ardyn's laughter. "They are a species of bioluminescent algae that attach themselves to the cavern walls, which are made of iron. I'm not certain why they've formed the way they have, but it may have something to do with air currents or moisture. I'm no geologist." 

He doesn't answer the last question but Prompto's forgotten about it anyway; he moves along the wall, all the way around the room, marveling at the colors and the oddly rhythmic pulses, like heartbeats. 

"Ardyn, this is gorgeous. I wish I had my camera." 

"Commit it to memory then, my dear prince. While I'm sure your photographs would be stunning, to remember and appreciate a thing with your senses can be even better."

"You're right," Prompto breathes, having made a full circuit and come back to stand on Ardyn's other side. He gazes up at the ceiling; all the little algae glow like kaleidoscopic stars, and he picks out brand new constellations in them that no one's ever seen before. Well, except for Ardyn. 

Prompto looks at him. Ardyn is watching him, smiling softly. It's neither dark nor light in the cave; the light spell has been extinguished and while Prompto can make out all his features, there's a dreamy sort of blur to them. His skin is colored by the algae: red on his cheek, purple on his forehead, sunset-orange on his stubbled chin; his normally claret hair is now indeterminably dark. Prompto wonders what his own face and hair look like under all these soft, dancing lights. It really is like being in a dream. And in dreams, you can pretty much do anything you want to. So Prompto does.

He closes the distance between them and kisses Ardyn, and Ardyn's mouth is warm and scratchy at the edges. It's not Prompto's first kiss, or even his second (those belong to Loqi and Aranea, respectively) but for the last few aching years he's been stupidly attracted to the chancellor.

 _His_ chancellor, when Prompto is emperor. And oh, doesn't _that_ suddenly have a new ring to it, and Prompto feels possessive of Ardyn all of a sudden, when he is hardly possessive of anything at all, having been free from an early age with his affections and lonely toys and spacious gilded cage. Ardyn has remarked enough upon Prompto's friendly nature that he wonders sometimes whether it is a compliment or a criticism, but he always says it with a curious sort of smile. 

Ardyn is smiling now, amused and thoughtful against Prompto's mouth, and before he can pull away Prompto finds more courage and grabs him by his clothes, clutching handfuls of scarves and wool and leather, and presses a more enthusiastic kiss to his lips. He is so nervous that he almost retreats immediately until he feels Ardyn's hands on him, one at his waist, the other at his cheek, his glove cold but his fingertips gentle, calloused. Prompto moves forward, wanting more contact, but is startled when Ardyn goes tense, having been backed up against the very pointy wall of the cave.

So maybe making a move in a cave full of sharp spikes wasn't Prompto's best idea. He blushes hard but hopes Ardyn can't tell in the dim fairytale lights. His words tumble out in a half-intelligible rush. "Do you think we can keep doing this but maybe in the car?" 

"In my car?" Ardyn smirks, like he somehow _knows_ the various scenarios Prompto has imagined. "But of course, my dear prince. Shall we?" He motions to the tunnel and lets Prompto lead them out. He doesn't have any spells so it's dark again, but the ground is easy enough to cover the second time around.

On the way down the slope Ardyn lets him take his hand again for balance, only Prompto doesn't let go when they reach flat terrain, and Ardyn kisses his knuckles like he's done a hundred times before, except this time there is promise in the brush of his lips against Prompto's glove.

The chill wind has picked up as evening approaches, whistling and nipping at Prompto's face. When they reach the car, Prompto stands up on his toes to wind his arms around Ardyn's neck. Before he can kiss him as he intends to, however, he slips on a patch of ice and clutches Ardyn tightly, laughing. 

"Graceful as a newborn spiracorn," Ardyn remarks dryly, but Prompto takes it in stride, because Ardyn proceeds with the kiss, deep and with enough filthy tongue to draw out a whimper. He's pressed against the car door and reaches back, fumbling for the handle, but Ardyn's hand is already there and he has to move so they can slide into the backseat. 

The interior of Ardyn's car is made of soft leather, obviously well-cared-for; the stitching is the same color as the curved seats, only a shade or two darker than Ardyn's hair, which Prompto finds hilarious and endearing. It's a sizeable vehicle, but with two people in it, especially one as big as Ardyn, it's almost cozy. Or maybe that's just because it's so familiar to Prompto, like the patterns of Ardyn's scarves or the low drawl of his voice. 

Ardyn leans over the front seats and uses his key to turn on the battery and the heater, setting his hat in the driver's seat. The car warms up slowly, making Prompto feel more languid as his limbs absorb the heat, like they're in front of a fire, snug and romantic. He remembers the soft lights and colors of the cave. 

Ardyn sits back and looks at Prompto with that curious smile, and Prompto finds the same nerve he found in that cave, crawling forward into Ardyn's lap, sighing when Ardyn wraps his arms around him. They kiss for awhile, Prompto taking cues from Ardyn, leaning his head to the side when the chancellor wants to kiss his jaw, his ear, his throat, as much bare skin as he can. Prompto's beanie is pulled off and a hand slides through his hair, petting. He takes his own hands away from grasping at Ardyn's coat long enough to remove his gloves, and he touches Ardyn's stubble, liking the prickly sensation. 

Ardyn murmurs something as Prompto feels a slight tug at his pants. "Hmm?" Prompto inquires lazily, leaning up to bury his face in Ardyn's messy hair. 

"Is this alright?" 

"Is what—oh!" Prompto jumps as he realizes Ardyn has undone the button of his pants and his zipper is halfway down, with only his underwear between his very aroused dick and the tips of Ardyn's fingers.

Ardyn stops moving and raises an eyebrow. "Are you—"

"No! No, it's fine, I'm fine, don't stop," he babbles. "Sorry, I'm just..."

"Nervous?" Prompto nods before he can deny the obvious. "We can go as slow as you need. We have," Ardyn kisses Prompto's nose, licks at his ear, "all the time," nibbles Prompto's lower lip, "in the world."

"Alright," Prompto nods again. "I mean, it's alright, you can...touch me."

Ardyn does take his time, though, dispersing kisses over Prompto's face as he pulls the rest of the zipper down, letting the pads of his fingers run up Prompto's twitching dick to the band of his underwear, then peeling those down and— 

"Oh fuck," Prompto gasps quietly, unable to stop himself from rocking forward into the warmth of Ardyn's hand, head falling onto Ardyn's shoulder, nuzzling his neck beneath his collar and he doesn't know if he says _oh fuck_ again or just thinks it but what Ardyn is doing feels _so good,_ infinitely better than what he does to himself late at night in his bedroom, fantasizing about exactly this—

"Ardyn, I—" He pants, trying to form words, but he's never really been good with those despite all the lessons and lectures on etiquette and enunciation and articulation, and it's definitely harder to be coherent with Ardyn squeezing behind the head of his cock just tightly enough to tease. " _Ardyn._ " 

Soft laughter, the fond kind, not the mocking kind. "Tell me what you want, my prince."

"I want you to say my name, _Chancellor,_ " Prompto huffs, sudden and capable, and Ardyn laughs again. 

"Prompto," he purrs, lips pressed to Prompto's temple, dragging down his cheekbone to his panting mouth, which he doesn't quite kiss. "Anything for you, dear Prompto."

Now that he's found his voice, Prompto is emboldened. "Anything, huh?" He pulls back a little, ignores his own low whimper when Ardyn trails calloused fingertips along the larger vein of his cock. "How about you fuck me properly?" 

"You truly are determined to make a mess of my car, aren't you?"

"You bet." Prompto's hips haven't stopped moving, mostly of their own accord and with continued encouragement from Ardyn's featherlight strokes. He wants to whine at the lack of pressure. "We can totally make a mess of my bed later if you want, you know, payback." 

"I'll keep that in mind." 

The hand on his cock is gone and Prompto does whine, until he realizes Ardyn is undressing him, pushing his coat off his shoulders and letting it slide onto the floor of the backseat. He tries to help but is batted aside, so he lets Ardyn lift his shirt over his head to join his discarded coat and hat and gloves, and he shivers despite the car's heater. He is manhandled onto his back on the leather seats — _finally,_ exactly where he imagined being earlier — and Ardyn shrugs out of his own coat and vests above him.

Prompto decides he ought to do something, and that something is to palm the front of Ardyn's pants, where he finds a cock significantly larger than his own but just as hard. Ardyn sucks in a breath, and Prompto looks up at him, grinning even though he's nervous, but the expression on Ardyn's face is priceless, and if Prompto had his camera he would so risk killing the mood to snap a photo of it. 

"Prompto, are you sure?" 

"Oh, definitely," Prompto nods, trying to spread his thighs as much as he is able with his pants still half-on and not as much room as he assumed between the seats, kneading his hand against Ardyn's cock again to make his answer as crystal clear as possible. "I am so, so sure about this, please..."

"Say it again." 

Ardyn's pupils are huge and black in rings of golden irises, searching Prompto's own, and he shivers once more under that intense gaze. "Please," he breathes, because he's not quite sure what Ardyn means so he goes with the most logical answer. "Fuck me." 

They work together to remove Prompto's boots and pants entirely, and although Ardyn undoes the top of his own striped pants he doesn't take them off. He leans across the front seat again, this time over the passenger side, and Prompto is confused as he hears the glove compartment click and some rummaging, until Ardyn returns with a vial of what looks to be a clear oily substance. _Oh._ Right. Prompto swallows around a sudden lump in his throat. He wants this. He wants Ardyn, who is coating his fingers liberally with the oil, then bending over Prompto once more, kissing him, stroking the inside of one thigh with his dry hand soothingly.

There is pressure where there's never been before, not like this, and Prompto's involuntary noise is muffled against Ardyn's mouth. Ardyn pulls back enough to murmur, "Relax. Stop me if it hurts." 

He feels one finger enter him slowly while Ardyn continues to rub comfortingly along his thigh and hip and chest, settling just for a moment directly over his heart before journeying back downward as he pushes in and out, thumb brushing Prompto's balls. It's...strange, but not bad. When he's taking Ardyn's finger easier another is added, a bit of a stretch, not quite a burn — Prompto dazedly recalls the length and dexterity of Ardyn's fingers during training exercises, wrapped around the hilt of his sword the way they had been around his cock. 

When Ardyn bends his fingers a certain way, Prompto cries out, hips surging and his thighs tightening around Ardyn's sides. This obviously encourages Ardyn to do it again, adding a third finger as he wraps his other hand around Prompto's dick again and pumps in time, eliciting a whimper and a slight flail, Prompto clutching at Ardyn's shoulder and scrabbling at the leather seat beneath him. He opens his eyes without realizing he's closed them, and sees he's being watched with a familiar knowing smirk. 

"Ardyn, I want..." Prompto nearly sobs. "Will you..."

"Will I what?" Ardyn is relentless, curling his fingers twice more, three times. 

"Please fuck me, please," Prompto begs, nails digging into Ardyn's back through his shirt, wishing it was skin. He feels bare because he is, more so than Ardyn, still almost decent aside from his open pants. 

Ardyn hums, smiles with teeth into the side of his neck. "Since you ask so nicely." He removes his fingers and applies more oil, uses it to slick his cock a few times. He hitches Prompto's thighs higher up his waist before pressing himself to Prompto's entrance and pushing. Prompto's hips jump and Ardyn tuts, holding them down. 

"Relax, my dear." 

Prompto tries his best, he does, he nods against Ardyn's shoulder and gasps when he feels Ardyn slide farther in. He squeezes his eyes shut and wonders if it isn't more than he can take, but he doesn't want to stop now. Ardyn pauses a few times, making little rocking motions that help ease him in until they're flush skin to skin, and Prompto can't do anything except breathe and shudder. 

It's a lot to process. Ardyn's dick is thicker, _more_ than his fingers, curved to fit inside Prompto in a way that feels full and weird and stings a little. He's heavy between Prompto's legs and the fabric of his clothes feels different against his oversensitive skin. 

"Ardyn..." Prompto's eyes flutter open and he looks up, not knowing quite what he means to say. He thinks he's ready for Ardyn to move now, and something in his expression must communicate that because Ardyn does, pulling back and pushing forward again, short thrusts, getting him used to it, making a gentle rhythm. Prompto wraps his arms around Ardyn's neck and kisses him because it's easy and it soothes his remaining nerves and the burning stretch seems to lessen. He opens his mouth to Ardyn's tongue and thinks in broken fragments that _Ardyn is fucking him, he's being fucked by Ardyn,_ and it's starting to feel pretty good.

Ardyn pulls almost all the way out and then thrusts in deep, lifting Prompto's ass clear off the leather seat, and Ardyn's hand slides down to grip him there, pulling Prompto up to meet his next few thrusts, until Prompto does it on his own with the limited leverage available to him. It sends little sparks up his spine when their hips meet, and Ardyn's shirt has rucked up enough that Prompto's cock is rubbing against Ardyn's warm belly each time, and the sensations are almost overwhelming. Prompto wants to keep kissing him, but he's breathing too hard and making high-pitched moans. Faintly, he hears Ardyn, too, making softer noises of pleasure after each of Prompto's, and then: 

" _Prompto._ "

He cries out and his dick jumps against Ardyn's belly, and Ardyn dutifully encircles it again, stroking quickly in contrast to his almost leisurely thrusts. Prompto comes before he is ready for it, gasping for breath, clinging to fistfuls of Ardyn's shirt and seeing stars behind his eyelids, the constellations of the cave.

He must have done something right because Ardyn comes too, after a few particularly hard thrusts, face buried in Prompto's neck so he can't see his expression but he can hear and feel the hot ragged moan against his already overheated skin. 

The cold outside seems so far away and so long ago, despite a meter of distance and less than an hour passing. 

Prompto tries to capture everything like a series of photographs: the way Ardyn holds some of his weight off Prompto but hasn't moved yet, their chests touching so that Prompto can feel both their heartbeats; the odd sticky warmth inside of him and drying between his and Ardyn's stomach, the way his thighs and his lower back ache; when Ardyn finally lifts his head and slides his stubbled cheek across Prompto's for a kiss.

It's lazy and sweet, and Ardyn is smiling, so Prompto smiles too. "So that was great," he sighs.

Ardyn hums in agreement. He pulls away and slips out of Prompto slowly, rummaging through his coat until he comes up with a handkerchief that he uses to clean both of them, and he gives only a cursory frown when he wipes the leather seat beneath Prompto's ass. "Worth it," Prompto says, almost a question, a bit of nervousness having creeped back now that it's all over. 

"Indeed," Ardyn smirks at him, humor making his amber eyes shine even as Prompto realizes it's getting dark outside. The sunless sky has turned a deeper grey-blue, and full night will be here soon. 

"I meant what I said about making a mess of my bed." He tries not to sound too hopeful. "I want...I want you to stay. When we get back." To the castle. To reality. To duty and stations and constraint.

Ardyn must hear the reticence and see it on his face — he sees everything, Prompto thinks, and not just because Prompto has always been terrible at hiding his feelings. Ardyn leans over and takes one his hands, kissing his knuckles with the same pedantic deference of always underneath the newfound promise of earlier. He holds Prompto's gaze. 

"Then stay I will," he vows, and he means more than what Prompto is asking for. He means until Prompto is no longer prince but Emperor Prompto Aldercapt, and Ardyn is his chancellor. 

Prompto swallows around the sudden tightness in his throat and chest and ignores the wetness gathering at the corners of his eyes, and grins up at Ardyn. 

"I am gonna rock your world, old man." 

Ardyn's rich deep laughter is cut off by Prompto sitting up to kiss him, and they wrap around each other for a little while longer, until it's well and truly dark outside, but Prompto remembers impossible light in a cave.


End file.
